Fix debug so that multithreaded output doesn't overlap (not needed here, just for consistency with other projects)

debug.cpp

@@ -10,7 +10,7 @@ Debug::Debug(int n) : lvl(n) {
 
 		indent.append(lvl - 1, '\t');
 		if (lvl > 1) indent.append("*** ");
-		std::cerr << indent;
+		buffer << indent;
 
 // 		std::time_t now = std::time(nullptr);
 // 		std::string dt = std::ctime(&now);
@@ -19,7 +19,7 @@ Debug::Debug(int n) : lvl(n) {
 }
 
 Debug::~Debug() {
-	if (lvl <= debug_level) std::cerr << '\n';
+	if (lvl <= debug_level) std::cerr << buffer.str() << '\n';
 }
 
 void Debug::set_debug_level(int n) { debug_level = n; }

debug.h

@@ -8,6 +8,7 @@ class Debug {
 private:
 	int lvl; // debug level of the particular instance of Debug stream
 	static int debug_level; // debug level set globally
+	std::stringstream buffer;
 
 public:
 	explicit Debug(int n);
@@ -20,7 +21,7 @@ public:
 	template <typename T>
 	Debug& operator<<(T const& value) {
 		if (lvl <= debug_level)
-			std::cout << value;
+			buffer << value;
 		return *this;
 	}
 	static void set_debug_level(int n);